The present invention relates to a zinc electroplating bath brightener and to improvements in the electrodeposition of zinc from aqueous acid plating baths containing the zinc brightener.
Heretofore, certain characteristics of conventionally utilized acid zinc bath formulations have rendered them in many instances somewhat impractical to use. For example, the bath formulations disclosed in U.S. Pat. No. 3,694,330, has a limiting factor in that only a rather low current density can be applied to a given article to produce a lustrous zinc deposit. Should the current density be raised to increase the speed of plating, very dark, coarse deposits of zinc would be plated on the article. Another common problem is that which occurs in using the bath formulations of U.S. Pat. No. 3,723,263 in that at bath temperatures of above 95.degree. F, the formulations encounter a severe loss of brightening ability.
Another prior art U.S. Pat. No. 3,723,263, and a division thereof, U.S. Pat. No. 3,767,540, both relate to aqueous acid zinc electroplating baths containing naphthol polyoxyalkylate in combination with polyethylenimine. These patents also state that aromatic aldehydes and ketones may be present. U.S. Pat. No. 3,729,394 relates to an acid zinc electroplating bath having dissolved therein a block copolymer of propylene oxide and ethylene oxide. The block copolymer may be utilized alone or in instances with a compound of N-(alkyl sulfonyl)glycine. Additionally, another U.S. Patent, namely U.S. Pat. No. 2,674,619, relates to polyoxyalkylene compounds which have an outstanding detergent and surface active properties and in which the hydrophobic element is a polyoxypropylene polymer having a molecular weight of at least 900.
The present invention relates to a zinc brightener which is not taught or suggested by the above prior art patents and, moreover, the present invention produces a synergistic result in that extremely bright and lustrous deposits of zinc are obtained from low through high current plating densities.